GENEVA —
With the first stage agreement to limit Iran's nuclear program finally achieved after a decade of dispute, diplomats will have little time to rest. They are on a six-month clock to reach a comprehensive agreement, a task they acknowledge will likely be even more difficult than reaching the interim accord.

It was a triumphant moment for the foreign ministers of Iran and the six-nation U.N. contact group, well after three in the morning on Sunday. But their hard-won moment of satisfaction won't last long. Even more difficult issues lie ahead, including permanent, verifiable limits on Iran's nuclear program and the potential lifting of all nuclear-related sanctions.

In spite of the show of camaraderie, there is still a serious shortage of trust, and skeptics in the West, the Gulf, Israel and elsewhere worry that with some relief from the sanctions in hand, Iran won't go any further.

From the Maplecroft risk assessment firm in Britain, Torbjorn Soltvedt told VOA that with sanctions being slightly eased, some countries could try to get around what's left.

“It is then clearly quite possible that the sanctions regime will erode and that Iran will play a long game and essentially advance the nuclear program so as to close the gap between a latent capability and a full blown nuclear breakout,” said Soltvedt.

But U.S. officials say that won't be so easy, with strong enforcement still in place, along with the most damaging of the sanctions.

Iran analyst Ali Vaez of the International Crisis Group agrees.

“The most important part of the sanctions regime, the crown jewels, which are the oil and financial sanctions, will remain in place. And therefore Iran will have the motivation to come back and negotiate the comprehensive agreement, which is much more difficult to negotiate and would require much more painful concessions,” said Vaez.

Indeed, the impact of the sanctions on ordinary Iranians is believed to be what propelled the relatively moderate candidate, Hassan Rouhani, to the presidency in last May's election, making this accord possible.

The former British ambassador to Iran, Richard Dalton, believes Iranian officials, including Supreme Leader Ayatollah Ali Khameini, have made a strategic decision to do what is necessary to put the nuclear dispute, and the economic sanctions, behind them.

“They will not be saying to themselves, 'We just have to sit this one out and we will emerge with an economy that can trade with the rest of the world freely.' I believe they will go all out in this six-month period to achieve a comprehensive agreement,” said Dalton.

But that doesn't mean it will be easy. Iran will be asked to give up much of the nuclear fuel enrichment program it has built over many years at great expense, and to allow intrusive inspections to prove it is not secretly trying to build a nuclear bomb.

There will likely be many more long days and nights of negotiations as the six-month deadline approaches.